I was just about to write more or less the same comment before I decided to refresh the page.

I just started coding as if I was working with a version of Typescript.

I only Google from time to time for the standard library docs.

Same here. it feels like a very generic algol family language, and if you're familiar with any of them it's almost trivial to pick up to the point where you can just sort of write it and figure things out as you go.

That was in fact the most pleasant things about Flutter for me, the language was a non-barrier.

for me there were only some syntactic sugar things I had to learn.

Yes but there is also the question why don't I learn React, Rust or Clojure instead of Dart. Am I going to be better of knowing Dart?

Dart is based on js and flutter is based on react. Going from js+react to dart+flutter will not be that difficult. Learn both.